This invention relates to a flat-stock, stamped knitting tool for textile machines, particularly knitting and warp-knitting machines. The knitting tool includes a shank, having at least one free space (hereafter "window opening") formed therein by shank edges having at least one region of reduced shank thickness. The window opening is filled with a heterogeneous material which is firmly connected to the shank and which projects into the region of reduced shank thickness.
By the term "knitting tool" latch needles, springbeard needles, compound needles, latchless needles such as plush hooks for producing plush material, as well as sinkers and the like are meant.
As explained in detail, for example, in U.S. Pat. No. 5,582,038 based on the prior art mentioned therein, stamped knitting tools are known that have at least one window opening formed in the shank, for example, in the shape of an elongated hole, whose longitudinal axis is parallel to or coincides with the longitudinal axis of the shank. The window opening is filled with a vibration-damping, heterogeneous material which is firmly connected to the needle shank. As a rule, the material is a flexible plastic having high damping characteristics, although other materials may be used instead.
The vibration behavior of the knitting tool is favorably influenced by the vibrating-damping material disposed in the window opening of the shank. It is feasible to divide the knitting tool into a highly elastic structure in which the longitudinal hole is delimited by two continuous vertical guide portions extending from the upper shank edge to the lower shank edge, and two narrow webs interconnecting the guide portions. The webs are arranged parallel to each other and have often a web height of no more than 1.1 mm. Such knitting tools may be used over long operational periods with high operational speeds, without the occurrence of an appreciable number of web or hook breakages due to material fatigue. Due to the fact that the window openings are filled-in and are thus not open, no lint or dirt deposits can collect therein which, depending on the operating conditions, is considered an advantage.
Since the vibration-damping material that fills the window opening can be effective only if it is firmly connected to the shank material along the edge of the window opening, additional measures have been previously taken to provide a form-locking anchoring of the plastic material, particularly for very thin knitting tools, which in operation are exposed to bending due to lateral forces in the region of the window opening. In this connection published European Application 282 647 discloses the profiling of the web and/or guide element regions that surround the window opening. The profiling can have zones of reduced wall thickness, which are either locally limited or which extend in a strip-like manner over the entire periphery of the window opening or a portion thereof. The zones of reduced wall thickness project into the plastic material which fills the window opening and contribute to a form-locking anchoring of the plastic material to the tool shank.
To facilitate the manufacture of knitting tools of the above-outlined type, particularly knitting needles with window openings having profiled regions of reduced shank thickness around the periphery of the window opening, the earlier-noted U.S. Pat. No. 5,582,038 discloses that the shank is, at least section-wise along the edge of the window opening, chamfered inwardly towards the window opening such that the chamfered regions project into the heterogeneous material that fills the window opening. The chamfered regions are, as a rule, embossed into the shank and are arranged on both sides of the shank.
It has been found in practice that embossing chamfered edges which, as viewed cross-sectionally, taper in a wedge-like manner towards the window opening, may involve difficulties in certain needle types. This is due to the fact that during the embossing of the edge region of the punched-out window opening, shank material is displaced outwardly from the window opening, thus resulting in an uneven material accumulation in the shank material that surrounds the embossed region. This, in turn, leads to undesirable configurational changes in the subsequently stamped-out knitting tool. This is so because, as a rule, when stamping such a knitting tool, the window openings are punched out first from a flat-steel ribbon and are subsequently embossed along the edge of the window opening, and thereafter the knitting tool itself is stamped out. If, in the course of the stamping operation the knitting tool, because of the preceding embossing operation, undergoes a lasting configurational change, for example, a change where the shank height in the region of the punched-out window opening is increased slightly relative to the stamping dimensions as the internal stress conditions are equalized, then complex reworking operations may be necessary.